1. Field of the Invention
This invention relates to piezoelectric actuators. More specifically, the invention relates to cylindrically-shaped and telescopically-extending piezoelectric fiber composite actuator assemblies.
2. Description of the Related Art
Piezoelectric fiber composite actuators are flexible, planar actuators that can be bonded to a structure and then operated to generate and control or detect deflections/strain of the structure. A conventional piezoelectric fiber composite actuator has the following structural features:
(i) a layer of individual piezoelectric fibers (e.g., round, square, etc.) arrayed side-by-side and typically encased in a polymer matrix material; and
(ii) interdigitated electrodes etched or deposited onto one or two polymer film layers with the resulting layers sandwiching the layer of piezoelectric fibers.
The layer of individual piezoelectric fibers can be assembled from individually-extruded piezoelectric fibers or can be formed from a macro sheet of polymer-backed piezoelectric material that has been processed (e.g., piezoelectric material that has been mechanically diced or etched, laser etched, etc.) to yield parallel rows of piezoelectric material “fibers” attached to the polymer backing. A piezoelectric fiber composite actuator constructed in this fashion is also known as a macro-fiber composite actuator. A complete description of such an actuator is disclosed in U.S. Pat. No. 6,629,341, the contents of which are hereby incorporated by reference.
The piezoelectric fiber/macro-fiber composite actuator is a flat device that is lighter and smaller than hydraulic or gas piston-cylinder actuators/assemblies as well as piezoelectric “stack” actuators/assemblies. However, when not bonded to a structure, piezoelectric fiber/macro-fiber composite actuators tend to buckle when used to generate or detect a strain, displacement or force in the plane of the actuator.